Are there any known connectivity issues with Tomato Shibby on an Asus RT-AC66U?

I'm experiencing periodic dropouts of internet connectivity and I don't know what is causing it. I've had separate 6 visits from engineers from my ISP (Virgin Media, UK) who have spotted various issues with the incoming signal and have performed various work in the cabinet on the street including replacing the amp in there. They've also replaced my cable modem, swapping a SuperHub2 for a SuperHub1 both of which I run in "Modem Mode" and wire into the WAN port of my AC66U. That swap was made on Thursday, now it's Monday and I've woken up to no internet access (no HTTP, "Request timed out" when trying to ping 8.8.8.8). The overview page in Shibby said the WAN was up and there was time remaining on the DHCP lease. Rebooting the modem didn't do anything. Rebooting the modem and router got back my internet access, so I'm wondering, is there any known issues in Tomato Shibby for the AC66U?

Check "IP Traffic->Last 24 Hours" and look for lots of outbound traffic — if you have other users on your router. Make sure in the list of local IPs above the graph that you click on "LAN (192.168.1.0)" so that you see the entire set of traffic from the users of your router.

Because you're sophisticated enough to have Shibby 1.28 like I have, and the exact same router model, I suspect you're already looked at that.

If you haven't yet, and you do have other users sharing your internet connection through your router — if someone is seeding a torrent, you will see that as spikes of outbound traffic — below the graph to the are the "TX" and "RX" symbols, each with a two-dash color bar beneath the 'TX' and 'RX' letters.

If you see a lot of output on the graph in the color of the 'TX' color band, you need to one-by-one click on the local IP addresses above the chart to find which user is doing all the uploading.

Is uploading a lot the only thing that can cause the symptoms you have? Nope.
But it's easy to check.

And because for whatever reason torrent users either don't know or care about the harmful effects of uploading a lot, 'seeding' to get enough points to be able to download — this is a very common cause of the symptoms you have.

I'm very sorry if this sounds all too pedestrian, obvious and so on, it's not my intention to be condescending, I simply don't know your level or any others who might read this.

We completely halted much of our connection problem by identifying then putting limits on the user on our Lan who despite our pleas continued to seed torrents in a huge way.